Environmental Legacy of redlining
What is the present-day impact of historic “redlining” of US cities during the Great Depression on ecological processes?
Environmental Justice and Ecology
Dr. Christopher Schell
Environmental Justice and Ecology
Context: Redlining
- The Home Owners’ Loan Corporation (HOLC) was a government-sponsored corporation created as part of the New Deal
- The HOLC created a housing appraisal system of color-coded maps that categorized the riskiness of lending to households in different neighborhoods
- Lower grades = less opportunity for loans but lower grades also = minority communities
- Red-lining: A discriminatory practice in which financial services are withheld from neighborhoods that have significant numbers of racial and ethnic minorities
- It was outlawed in 1968 following the passage of the civil rights bill.
Context: Canopy cover
- Trees and vegetation influence the local temperatures
- Generally: more trees/canopy, cooler local temperatures
Data: satellites
Vegetation indices from satellites
Data: Satellites
Satellites record reflected light in different regions of the light spectrum (wavelengths)
Data = a value of average intensity over a window of wavelengths (“band”)
Bands are chosen because they measure different aspects of the environment.
Data: Satellites
![diagram of spectral bands measured by Sentinel 2]()
Data: Indices
- Bands can be combined to get indices that measure ecological processes
- Normalized Difference Vegetation Index (NDVI) ~ photosynthesis (amount + health of vegetation)
- Higher NDVI = more canopy = cooler local temperatures
Data: Raster
Band and NDVI across space are stored as rasters
Data: Data Cubes
Rasters are combined over time to form data cubes
Data: COGs and GeoTIFFs
Full remote sensing data sets are huge! (many bands, locations, times)
Data: COGs and GeoTIFFs
- A Cloud Optimized GeoTIFF (COG) is a regular GeoTIFF file aimed at being hosted on an HTTP file server with an internal organization that enables more efficient workflows on the cloud.
- Leverages the ability of clients to request just the parts of a file they need. (https://cogeo.org)
- GeoTIFF is a public domain metadata standard that allows georeferencing information to be embedded within a TIFF file (https://en.wikipedia.org/wiki/GeoTIFF)
Environmental Justice and Ecology
Assignment
- Calculate, map, and analyze NDVI for different redlining grades within Richmond, VA
- Calculate and map NDVI for different redlining grades for five cities of your choice
- Evaluate how the relative influence of redlining varies across environmental or demographic gradients
Assignment
- Review tutorial
env-justice-tutorial.qmd
- Assignment is in
assignment/env-justice.qmd
Data Science Skills
- Cloud access of remote sensing data
- Raster Cubes
- Linking rasters with polygons
- Calculating spatial statistics within polygons.